What is the scientific definition of mass?

Mass is the measure of the amount of matter an object contains, and it represents the number of atoms in an object. The basic unit of mass is the kilogram.

Newton's Second Law of Motion states that when force is applied to a mass, acceleration is produced. The more mass an object has, the more force is needed to produce acceleration in the object. In this way, mass is often described as the property of an object that resists acceleration. Mass is not dependent on gravity so it is not the same as its but is proportional to its weight.